<template>
  <div class="type-nav">
    <div class="container">
      <div @mouseenter="navIsEnter = true" @mouseleave="navIsEnter = false">
        <h2 class="all">全部商品分类</h2>
        <div v-show="sortIsShow" class="sort">
          <div  @click="toSearch" class="all-sort-list2" @mouseleave="itemMouseLeaveCategory" @mouseenter="isLeave=false">
            <div :class="categoryIndex===index?'active':''" @mouseenter="itemMouseEnterThrottle(index)" class="item" v-for="(categoryOne,index) in categoryList" :key="categoryOne.categoryId">
              <h3>
                <a :data-category1Id="categoryOne.categoryId"
                   :data-categoryName="categoryOne.categoryName"
                >{{categoryOne.categoryName}}</a>
              </h3>
              <div class="item-list clearfix">
                <div class="subitem">
                  <dl class="fore" v-for="categoryTwo in categoryOne.categoryChild" :key="categoryTwo.categoryId">
                    <dt>
                      <a :data-category2Id="categoryTwo.categoryId"
                         :data-categoryName="categoryTwo.categoryName">{{categoryTwo.categoryName}}</a>
                    </dt>
                    <dd>
                      <em v-for="categoryThree in categoryTwo.categoryChild" :key="categoryThree.categoryId">
                        <a :data-category3Id="categoryThree.categoryId"
                           :data-categoryName="categoryThree.categoryName">{{categoryThree.categoryName}}</a>
                      </em>
                    </dd>
                  </dl>
                </div>
              </div>
            </div>
          </div>
        </div>
      </div>
      <nav class="nav">
        <a href="###">服装城</a>
        <a href="###">美妆馆</a>
        <a href="###">尚品汇超市</a>
        <a href="###">全球购</a>
        <a href="###">闪购</a>
        <a href="###">团购</a>
        <a href="###">有趣</a>
        <a href="###">秒杀</a>
      </nav>
    </div>
  </div>
</template>

<script>
import {mapActions, mapState} from "vuex";
import {throttle} from "lodash";

export default {
  name:'TypeNav',
  data() {
    return {
      categoryIndex: -1,
      isLeave:true,     // 默认不在指定区域内
      navIsEnter:false   //保存三级分类区域整体区域,是否鼠标移入
    }
  },
  mounted() {
    // 挂载时 获取异步的首页三级列表数据
    this.getCategoryList()
    // console.log(this.categoryList)

    // 挂载时 使用throttle方法 把鼠标移入的事件函数itemMouseEnter 封装成一个节流函数并返回
    this.itemMouseEnterThrottle = throttle(this.itemMouseEnterCategory,300,{
      leading:true,   // 指定调用在节流开始前
      trailing:true   // 指定调用在节流开始后
    })
  },
  methods:{
    ...mapActions('category',['getCategoryList']),

    // 鼠标移入事件
    itemMouseEnterCategory(index){
      //因为使用lodash有一些bug
      //leading配置肯定必须是true
      //trailing配置如果是false,则鼠标在节流期间移入某个元素停留,这个元素可能不会获取焦点
      //trailing配置如果是true,则鼠标移出整个三级分类的时候,最后一个路过的列表可能会在节流后触发一次
      //我们就配置trailing为true,在核心代码触发前做一个判断,是否鼠标已经移出整个区域

      if (this.isLeave) return    // 如果不在指定区域内  就 不会显示 移入的效果

      this.categoryIndex = index;

      // 按道理来说这里应该发送请求 获取二级列表数据 (后端返回的数据有问题)
      // ...

    },
    // 鼠标移出事件
    itemMouseLeaveCategory(){
      this.isLeave = true;
      this.categoryIndex = -1;
    },

    // 节流后的鼠标移入三级列表的事件函数  （防止多发送ajax请求  提高浏览器性能）
    itemMouseEnterThrottle:()=>{}    // 初始函数
    ,
    // 编程式导航 跳转页面
    toSearch(e){
      const {
        categoryname: categoryName,
        category1id: category1Id,
        category2id: category2Id,
        category3id: category3Id,
      } = e.target.dataset

      console.log(e.target.dataset);
      //判断当前点击的是不是a元素,如果不是直接退出,通过categoryName来判断
      if (!categoryName) return;

      // 获取搜索框的params参数合并
      const params = this.$route.params

      this.$router.push({
        name:"Search",
        query: {
          categoryName,
          category1Id,
          category2Id,
          category3Id,
        },
        params
      })
    },
  },
  computed:{
    ...mapState('category',['categoryList']),
    //得到一个值,决定下拉列表是显示还是隐藏
    sortIsShow() {
      //如果当前是home页,一定是显示的
      if (this.$route.name === "Home") return true;

      //判断鼠标是否移入移除整体的nav
      return this.navIsEnter;
    },
  },
  watch: {
    //一旦路由发生变化,恢复nav的隐藏状态
    $route() {
      this.navIsEnter = false;
    },
  },
}
</script>

<style scoped lang="less">
.type-nav {
  border-bottom: 2px solid #e1251b;
  .container {
    width: 1200px;
    margin: 0 auto;
    display: flex;
    position: relative;

    .all {
      width: 210px;
      height: 45px;
      background-color: #e1251b;
      line-height: 45px;
      text-align: center;
      color: #fff;
      font-size: 14px;
      font-weight: bold;
    }

    .nav {
      a {
        height: 45px;
        margin: 0 22px;
        line-height: 45px;
        font-size: 16px;
        color: #333;
      }
    }

    .sort {
      position: absolute;
      left: 0;
      top: 45px;
      width: 210px;
      height: 461px;
      position: absolute;
      background: #fafafa;
      z-index: 999;

      .all-sort-list2 {
        .item {
          h3 {
            line-height: 30px;
            font-size: 14px;
            font-weight: 400;
            overflow: hidden;
            padding: 0 20px;
            margin: 0;

            a {
              color: #333;
            }
          }

          .item-list {
            display: none;
            position: absolute;
            width: 734px;
            min-height: 460px;
            background: #f7f7f7;
            left: 210px;
            border: 1px solid #ddd;
            top: 0;
            z-index: 9999 !important;

            .subitem {
              float: left;
              width: 650px;
              padding: 0 4px 0 8px;

              a{
                cursor:pointer;
              }

              dl {
                border-top: 1px solid #eee;
                padding: 6px 0;
                overflow: hidden;
                zoom: 1;

                &.fore {
                  border-top: 0;
                }

                dt {
                  float: left;
                  width: 54px;
                  line-height: 22px;
                  text-align: right;
                  padding: 3px 6px 0 0;
                  font-weight: 700;
                }

                dd {
                  float: left;
                  width: 415px;
                  padding: 3px 0 0;
                  overflow: hidden;

                  em {
                    float: left;
                    height: 14px;
                    line-height: 14px;
                    padding: 0 8px;
                    margin-top: 5px;
                    border-left: 1px solid #ccc;
                  }
                }
              }
            }
          }

          &.active {
            h3{
              cursor:pointer;
              background-color: lightskyblue;
            }
            .item-list {
              display: block;
            }
          }
        }
      }
    }
  }
}
</style>